Abstract: A method for reducing recalcitrant chemical oxygen demand (COD) of a liquid in a water system is provided. The method comprises pretreating the liquid in a pretreatment unit (12) to remove indigenous bacteria or microbes to a population level below which the indigenous organisms can interfere with the screened and externally introduced microorganisms. The liquid is then provided to a reactor (20) that has a filter bed (22) formed with a carrier material (26). Special microbes are screened and used to colonize the carrier material (26) to remove recalcitrant COD. A biofilm is cultured on the surface of the carrier material (26) to immobilize the screened microbes in the reactor (20). The method further comprises adding a co-substrate as the liquid enters the reactor (20) and percolating the liquid through the filter bed (22) colonized with the screened microbes to degrade at least part of the recalcitrant COD under aerobic conditions.

Abstract: A method for reducing recalcitrant chemical oxygen demand (COD) of a liquid in a water system is provided. The method comprises pretreating the liquid in a pretreatment unit (12) to remove indigenous bacteria or microbes to a population level below which the indigenous organisms can interfere with the screened and externally introduced microorganisms. The liquid is then provided to a reactor (20) that has a filter bed (22) formed with a carrier material (26). Special microbes are screened and used to colonize the carrier material (26) to remove recalcitrant COD. A biofilm is cultured on the surface of the carrier material (26) to immobilize the screened microbes in the reactor (20). The method further comprises adding a co-substrate as the liquid enters the reactor (20) and percolating the liquid through the filter bed (22) colonized with the screened microbes to degrade at least part of the recalcitrant COD under aerobic conditions.